As magnetic recording media have recently been used for increasingly high density recording, the so-called thin metal film type magnetic recording media have drawn increasing attention, instead of coated type magnetic recording media.
However, it is difficult to add a lubricating agent and an abrasive agent into a magnetic layer of a thin metal film type magnetic recording medium such as is typically done in coated type magnetic recording media. Therefore, thin metal film type magnetic recording media have shown poor durability, and in the case of a perpendicular magnetic recording disk having a Co-Cr alloy film, cohesion between the alloy film and a magnetic head usually takes place after about 100 passes and running cannot be continued.
It has been proposed to remove the above problem that a liquid lubricating agent is coated on the surface of a magnetic layer and that a solid protective layer is provided on the surface of a magnetic layer. Particularly, provision of a protective layer mainly comprised of carbon as a solid lubricating agent on the surface of a magnetic layer is effective to improve running durability, as disclosed in Japanese Patent Publication No. 33521/79.
However, such has still been insufficient to provide a fully satisfactory protective layer. The reason is believed to be that the dust and contaminants present on a magnetic head increase the friction coefficient between the head and a protective layer.
Further, it has also been proposed to include transition metal elements, boron, or silicon in a diamond type carbon protective layer, as disclosed in Japanese Patent Application (OPI) No. 29936/85 (the term "OPI" as used herein refers to a "published unexamined Japanese patent application"). However, lubricating properties are poor, and therefore sufficient durability still cannot be obtained.